A Blood Test For Depression Shows The Illness Is Not A Matter Of Will

A new test that identifies particular molecules in the blood could help doctors diagnose patients with clinical depression, according to a new study published in the journal Translational Psychiatry. The blood test can also predict which therapies would be most successful for patients, and lays the groundwork for one day identifying people who are especially vulnerable to depression -- even before they’ve gone through a depressive episode.

But perhaps just as important, said lead investigator Eva Redei, Ph.D., is the potential the test has for taking some of the stigma out of a depression diagnosis. When depression can be confirmed with a blood test like any other physical ailment, she said, there’s less stigma about having the disease and getting treatment.

“I really believe that having an objective diagnosis will decrease stigma,” Redei, a neuroscientist and professor at the Northwestern University Feinberg School of Medicine, told The Huffington Post. “Once you have numbers in your hand, you can identify that [depression] is an illness -- not a matter of will.”

The most effective way to treat depression is to treat it early, but past studies show that it takes an average of two to 40 months to diagnose depression -- if it gets diagnosed at all. Redei’s depression blood test could lead to faster and more accurate diagnoses, thereby transforming the way depression is treated.

If Redei’s findings are independently replicated and confirmed, then approved by the Food and Drug Administration, laboratories across the U.S. could incorporate the test into their battery of routine exams. This is in contrast to MDDScore, a depression blood test owned by Ridge Diagnostics that was announced in 2012. Because the test is proprietary to Ridge Diagnostics, doctors have to submit samples to the company’s lab in North Carolina, where the company analyzes the blood and sends back results. Redei's test, however, "can be done by any clinical laboratory anywhere, just like a cholesterol test,” Redei explained. “That is, assuming that we can go through the FDA approval [process] fast.”

Redei’s study compared the blood samples of 32 patients who had been diagnosed with depression in the traditional way (a clinical interview) with samples taken from 32 people without depression. She found nine RNA blood markers -- the molecules that carry out DNA's instructions -- that differed significantly between the two groups, which she then used as the basis for the depression diagnosis.

Then, the depressed patients went through 18 weeks of cognitive behavioral therapy, a common treatment for depression. Re-testing their blood, Redei was able to tell which patients had benefitted the most from therapy, just by examining the changes in their RNA markers. In other words, the test was also a biological way to tell if treatment had been effective.

Finally, Redei also noticed that there were three RNA markers that didn’t change in depressed patients, no matter if they had benefitted from cognitive behavioral therapy or not. She suspects they may be markers that show if a person is predisposed to depression.

"Being aware of people who are more susceptible to recurring depression allows us to monitor them more closely,” said David Mohr, Ph.D., co-lead author of the study in a press release. “They can consider a maintenance dose of antidepressants or continued psychotherapy to diminish the severity of a future episode or prolong the intervals between episodes.”

Zachary Kaminsky, Ph.D., of the Mood Disorders Center at Johns Hopkins Medicine, wasn’t involved with the study but is excited about its potential implications for depression treatment. Kaminsky is a pioneer in blood tests to predict suicide risk, and although he and Redei measure very different things in their tests, he sees that both researchers have similar goals when it comes to creating biological tests for mental illnesses.

“It’s an exciting time -- there is potential to find factors that are going to distinguish between various mental illnesses as well as responses to direct clinical treatment,” said Kaminsky to HuffPost. “Any finding that gets us closer to that is very interesting and worth following up.”

But Kaminsky also pointed out that Redei and Mohr’s research still needs to be independently validated by other patient populations to confirm that it works. For instance, Kaminsky pointed out, the study would have been more scientifically rigorous if it had used a different patient group to confirm the blood test, as opposed to using the same participants to both create and then test the predictions.

"I think this is very early stage and this model needs to be investigated in an independent sample,” Kaminsky said. “It will be important to test the predictability of these expression measures in independent cohorts.”

Redei acknowledged that the next step in research would be to run the tests on larger samples in order to validate the models and then submit them for FDA approval.

“The major question here is always funding,” said Redei. “We are really trying to gather as much funding from as many sources as possible so it can move ahead."

Major depressive disorder affects an estimated 6.7 percent of the U.S. population and is the leading cause of disability for Americans ages 15 to 44, according to the Anxiety and Depression Association of America. Despite the research hurdles she still needs to overcome, Redei is confident that her test can make a positive impact on the millions who struggle with depression -- not only by making treatment more precise, but by bringing psychiatry "into the 21st century,” Redei said. “We’ll get to the point where there won’t be any discrimination between physical illness and mental illness.”